This invention relates to improved adhesion of water-based inks and paints to articles made from heat stabilized halogen-containing resins. It relates particularly to articles of manufacture such as flexible film and semi-rigid tubing that are prepared from heat-stabilized vinyl chloride polymers.
Changes in heat stabilizers and in printing inks over the years has resulted in a loss of printability of flexible poly(vinyl chloride) substrates. The curtailment of heavy metals (e.g. cadmium) in stabilizers and of volatile solvents in both stabilizers and printing inks has been held responsible for the loss of printability. Thus, there has arisen a need for a way to enhance the wettability of such present day PVC substrates.
A patent application by Witco Corporation published under the number WO96/15186 teaches that the wettability of heat-stabilized PVC film to water-based inks and the adherence of such inks to the film are improved by the incorporation of oxidized polyethylene in the PVC composition. The heat stabilizer is a mixture of barium and zinc carboxylates having up to 20 carbon atoms in combination with organic phosphites.
The surface tension of a heavy metal-containing PVC has been found to be from 25 to 33% higher than that of a traditionally plasticized PVC according to E. R. Napoleon in xe2x80x9cJournal of Vinyl and Additive Technologyxe2x80x9d, 3, No. 2, 145 (June 1997).
As taught in co-pending, commonly assigned patent application Serial No. 09/133,605, filed August 13, 1998, the teachings of which are incorporated herein by reference, the degradation products of a blocked or latent mercaptan present during processing of the halogen-containing resin at an elevated temperature enhance the activity of metal-based heat stabilizers such as organotin carboxylates and mercaptides in the composition. Vinyl chloride resin compositions and articles made thereof are stabilized particularly well by a combination of very low levels of zinc carboxylates and latent mercaptans selected from the group consisting of 2-S-(hydroxyalkylthio)tetrahydropyran, 5-S-(hydroxyalkylthio)tetrahydrofuran, 6-S-(2-formylhydroxyalkylthio)tetrahydropyran, the carboxylic acid esters of said alcohols, and mixtures of said alcohols and esters. Said latent mercaptans are also referred to as 2-S-(tetrahydropyranyl)-thioalkanol; 2-S-(tetrahydropyranyl)thioalkyl carboxylate; 6-S-(2-formyl-tetrahydropyranyl)thioalkanol and carboxylates thereof, and their furanyl homologs, i.e., 5-S-(tetrahydrofuranyl)thioalkanol, and 5-S-(tetrahydrofuranyl)thioalkyl carboxylate.
It has now been found that a combination of such a latent mercaptan and a zinc salt of oxidized polyethylene is particularly valuable in that it imparts improved hydrophilicity to the surfaces of articles made from vinyl chloride resins as well as thermal stability during high temperature processing during fabrication of such articles. The zinc salt is the only metal-containing stabilizer present during the high temperature processing.
It is an object of this invention, therefore, to provide a heat stabilizer composition which is free from metals other than zinc and which also improves the wettability of vinyl chloride resins by water-based inks and paints.
It is another object of this invention to provide a heavy metal-free, heat stabilized halogen-containing resin having a surface tension which is amenable to coating with a water-based ink or paint.
It is a related object of this invention to provide heat stabilized flexible, semi-rigid, and rigid PVC resin articles which have improved receptivity to water-based inks and paints.
It is a related object of this invention to provide novel latent mercaptans which are useful, alone or in combination with other additives, in heat stabilizer compositions.
These and other objects of the invention which will become apparent from the following description are achieved by adding a heavy metal-free heat stabilizer comprising a latent mercaptan and a synergistic amount of a zinc salt of oxidized polyethylene as the sole metal-containing stabilizer to a vinyl chloride resin and processing the resulting composition at the incipient resin decomposition temperature whereupon a small but hydrophilically effective amount of oxidized polyethylene is split from the zinc salt by liberated hydrogen chloride and the latent mercaptan degrades to liberate a free mercaptan. Examples of the latent mercaptan include, without limitation, 2-S-(tetrahydropyranyl)thioalkanol, a carboxylate thereof, a 2-S-(tetrahydropyranyl)thiocarboxylic acid or ester thereof, furanyl homologs of each, and mixtures thereof.
For the purposes of this invention, the terms blocked mercaptan and latent mercaptan are used interchangeably to mean a thioether which degrades during processing of the composition at an elevated temperature to liberate a free mercaptan.
Other products of the degradation of the blocked mercaptan are believed to include carbocations of the blocking moiety which are stabilized by a molecular structure in which the electron deficiency is shared by several groups. Resonance stabilization and neighboring group stabilization are two of the possible mechanisms by which the carbocations may be stabilized. The carbocations act as intermediates in the formation of stable compounds early in the hot processing of halogen-containing polymers. Although such mechanisms and the resultant carbocations are believed to be an impetus for the liberation of the active free mercaptan, this invention is in no way limited by the foregoing attempt to explain the working of the invention. Those skilled in the art will see the resonance stabilization and neighboring group stabilization that are possible in the following structures of the blocked mercaptan; other mechanisms may be at work in other blocked mercaptans represented by these structures that also liberate an active free mercaptan upon thermal and/or chemical degradation during processing of polymeric compositions containing such blocked mercaptans.
The vinyl chloride resins, also referred to hereinafter as PVC resins, are made from monomers consisting of vinyl chloride alone or a mixture of monomers comprising, preferably, at least about 70% by weight of vinyl chloride, based on the total monomer weight. Examples of the copolymers include those made from vinyl chloride and from about 1 to about 30% of a copolymerizable ethylenically unsaturated material such as vinyl acetate, vinyl butyrate, vinyl benzoate, vinylidene chloride, diethyl fumarate, diethyl maleate, other alkyl fumarates and maleates, vinyl propionate, methyl acrylate, 2-ethylhexyl acrylate, butyl acrylate and other alkyl acrylates, methyl methacrylate, ethyl methacrylate, butyl methacrylate and other alkyl methacrylates, methyl alpha-chloroacrylate, styrene, trichloroethylene, vinyl ketones such as vinyl methyl ketone and vinyl phenyl ketone, 1-fluoro-2-chloroethylene, acrylonitrile, chloroacrylonitrile, allylidene diacetate, chloroallylidene diacetate, and vinyl ethers such as vinyl ethyl ether, vinyl chloroethyl ether, vinyl phenyl ether, and the vinyl ether of ethoxytetrahydropyran prepared by the reaction of one mole of acrolein with one mole of ethylene glycol divinyl ether. Typical copolymers include vinyl chloride-vinyl acetate (96:4 sold commercially as VYNW), vinyl chloride-vinyl acetate (87:13), vinyl chloride-vinyl acetate-maleic anhydride (86:13:1), vinyl chloride-vinylidene chloride (95:5); vinyl chloride-diethyl fumarate (95:5), and vinyl chloride 2-ethylhexyl acrylate (80:20).
As used herein, the term PVC composition means a composition comprising a vinyl chloride resin. A rigid PVC composition is one which does not contain a plasticizer. A semi-rigid PVC composition is one which contains from 1 to about 25 parts of a plasticizer per 100 parts by weight of the vinyl chloride resin. A flexible PVC composition contains from about 25 to about 100 parts per 100 parts by weight (phr) of the vinyl chloride resin. Alkyl esters of carboxylic acids in which there are from 1 to 3 alkyl groups having from 8 to 12 carbon atoms are representative of the plasticizers. The alkyl group may be n-octyl, 2-ethylhexyl, nonyl, decyl, or dodecyl. Suitable esters include phthalates, trimellitates, benzoates, adipates, glutarates, and sebacates. The plasticizer may also be a pentaerythritol or such an ester thereof. A polymeric plasticizer is also suitable.
As used herein, an acyloxyalkyl radical originates from a carboxylic acid ester of an alkyl alcohol. Therefore, the R1 radical of the stearic acid ester of mercaptopropanol, as represented by the formula below, is the stearoyloxypropyl radical; likewise, the R1 radical of the oleic acid ester of mercaptopropanol, which is one of the tallate esters of that alcohol, is the oleoyloxypropyl radical.
As used herein, substantially means largely if not wholly that which is specified but so close that the difference is insignificant.
One of the advantages of this invention is that the offensive odor of mercaptans is masked by a blocking group so that the latent mercaptan thus created may be put into a PVC composition or the like with little or no offense to the operator with the knowledge that the free mercaptan will be released as a degradation product when the treated composition is heated during the usual processing, e.g. extrusion. It is believed that the free mercaptan is consumed as it is liberated in response to the evolution of hydrogen chloride at the incipient decomposition temperature of the vinyl chloride resin.
The blocking compounds are preferably those which are capable of furnishing a stabilized carbocation having a molecular structure in which the electron deficiency is shared by several groups. Resonance stabilization and neighboring group stabilization are two of the possible mechanisms by which the carbocations may be stabilized. Blocking compounds such as 3,4-dihyropyran and 2,3-dihydrofuran are preferred for the purposes of this invention.
The blocked mercaptans suitable for the purposes of this invention are represented by the following formula: 
wherein a is 1, m is 0, and n is 0 or 1; y=1 to 4; R1 is Rxe2x80x2C(O)OH wherein Rxe2x80x2 is alkylene; or R1 is an alkyl, pentaerythrityl, alkylene, cycloalkyl, cycloalkylene, aryl, alkaryl, aralkyl, aralkylene, hydroxyalkyl, dihydroxyalkyl, alkoxyalkyl, acyloxyalkyl, hydroxy(polyalkoxy)alkyl, hydroxy(polyalkoxy)carbonylalkyl, acyloxy(hydroxyalkyl), acyloxy(alkoxyalkyl), acyloxy(polyalkoxy)alkyl, acyloxy(polyalkoxy)carbonylalkyl, alkoxycarbonylalkyl, oxy[bis(alkoxycarbonylalkyl)], oxy[bis(polyalkoxycarbonylalkyl)], benzoyloxy(polyalkoxy)alkyl, benzoyloxy(polyalkoxy)acyl, or alkylene bis-(acyloxyalkyl), thio-bis-[alkoxyacyl], dithio-bis-[alkoxyacyl], alkoxy(polyalkoxy)acyl, hydroxyalkoxyalkyl, alkoxy(hydroxyalkyl), alkoxy(polyalkoxy)alkyl, mercaptoalkyl, mercaptoalkylene, mercaptoalkoxycarbonylalkyl, tetrahydopyranyloxy(polyalkoxy)carbonylalkyl, tetrahydropyranyloxyalkyl, hydroxyaryl, or mercaptoaryl radical, said alkyl, alkylene, alkoxy, and acyl radicals having from 1 to 22 carbon atoms; R2, R3, R4, R5, R6, and R7 are independently hydrogen, a hydroxyl, mercapto, alkyl, alkylene, acyl, aryl, haloaryl, alkaryl, aralkyl, hydroxyalkyl, alkenyloxyalkoxy, alkoxy, aryloxy, alkaryloxy, mercaptoalkyl, hydroxyalkylmercaptoalkyl, mercaptoalkylene, hydroxyaryl, alkoxyaryl, alkoxyhydroxyaryl, arylcarbonyl, or mercaptoaryl radical having from 1 to 22 carbon atoms; X is a heteroatom selected from the group consisting of oxygen and sulfur, and one or both of the R3 and R5 alkylene radicals joins with R7 and X to form a heterocyclic moiety with X as the heteroatom.
The mercaptans useful in this invention include the well-known mercaptoalkanols and the carboxylate esters thereof, including, but not limited to, the following compounds: 
wherein
R10 and R19 are independently OH, xe2x80x94O(Cxe2x95x90O)R17 xe2x80x94(Cxe2x95x90O)OR17, xe2x80x94SH, aryl, C1 to C18 alkyl, and xe2x80x94H;
R11 is xe2x80x94H, aryl, or C1 to C18 alkyl;
R17 is xe2x80x94H, alkyl, alkenyl, aryl, aralkyl, alkaryl, cycloalkyl, or cycloalkylenyl;
wherein i=0 or an integer from 1 to 6 inclusive.
Mercaptan-containing organic compounds preferred as intermediates in the preparation of the latent mercaptans of this invention are those compounds according to formula (MC1) where R11 is xe2x80x94H, R19 is xe2x80x94H, R10 is xe2x80x94O(Cxe2x95x90O)R17 or xe2x80x94(Cxe2x95x90O)OR17, and i=1; and those compounds according to formula (MC3) where R11 is xe2x80x94H and i=1.
Examples of mercaptan-containing compounds described by the above formulas include, but are not limited to, the following compounds: 
In general, the procedure for making the latent mercaptans which are useful in this invention comprises adding the mercapto group of the free mercaptan across the double bond of a polarized, unsaturated compound as follows:
To a stirred mixture, under nitrogen atmosphere, of the mercaptan, acid catalyst, and optionally, a small percentage of antioxidant to inhibit radical reactions, is added dropwise to the polarized, unsaturated compound, either neat or in solution, while maintaining the temperature between 10-70xc2x0 C. The mixture or solution is then heated for between 1 and 6 hours at 35xc2x0-70xc2x0 C. and conversion to product is monitored by gas chromatography and iodine titration for SH. The acid catalyst is removed by an alkaline wash and the resulting product is dried with magnesium sulfate and filtered. The solvent, if required, is removed under reduced pressure at  less than 50xc2x0 C. to yield the latent mercaptan. A solid phase catalyst may be used and then filtered out of the reaction mixture and regenerated for use in a subsequent synthesis, In this way, a wash step is eliminated. This generalized procedure is referred to hereinafter as Procedure A.
In accordance with Procedure A, for example, mercaptoethanol is added across the double bond of N-vinylcaprolactam to yield N-2-hydroxyethylthioethylcaprolactam. Mercaptoethyldecanoate (or mercaptoethylcaproate) reacts with 3,4-dihydropyran in that procedure to give 2-S-(tetrahydropyranyl)thioethyldecanoate. Bis(hydroxyethylthioethyl)cyclohexyl ether is made from the mercaptoethanol and cyclohexyl di-vinyl ether. In like manner, the corresponding caprate, oleate, and tallate esters form the corresponding cyclohexyl ethers. Also, indene is converted by the addition of the mercaptoethanol to 2H-dihydroindenylthio-ethanol.
A generalized procedure for the condensation of a free mercaptan with a labile halogen-containing compound is as follows:
To a stirred mixture of the mercaptan and halogen-containing compound under nitrogen atmosphere is added dropwise a solution of sodium methoxide in methanol while maintaining the temperature below 50xc2x0 C. optionally, the reaction is allowed to proceed without the addition of a base source and the liberated hydrogen chloride is removed by nitrogen gas sweep and neutralized with the use of an external acid scrubber. The mixture or solution is then heated for between 2 to 24 hours at 50xc2x0-70xc2x0 C. and conversion to product is monitored by gas chromatography and iodine titration for %SH. The product is then neutralized, washed with water, dried with magnesium sulfate, and filtered. The solvent, if required, is removed under reduced pressure at  less than 50xc2x0 C. to yield the latent mercaptan. This generalized procedure is referred to hereinafter as Procedure B.
A generalized procedure for the condensation of a free mercaptan with a labile hydroxyl-containing compound is as follows:
To a stirred solution of the mercaptan, acid catalyst, and solvent under nitrogen atmosphere is added the hydroxy-containing compound either neat or in solution while maintaining the temperature  less than 45xc2x0 C. The solution is then heated to 45xc2x0-75xc2x0 C. for between 1 to 10 hours and conversion to product is monitored by gas chromatography and iodine titration for %SH. Optionally, an azeotropic solvent is chosen for removal of reaction water by an appropriate means at reflux temperatures, typically 60xc2x0-120xc2x0 C. Completion of reaction is achieved after the theory amount of water has been collected. The acid catalyst is removed by alkaline wash and the resulting solution is dried with magnesium sulfate and filtered. The solvent is removed under reduced pressure at  less than 55xc2x0 C. to yield the latent mercaptan. This procedure is referred to hereinafter as Procedure C.
For example, 2-hydroxybenzyl alcohol condenses with mercaptoethanol in accordance with Procedure C to form 1-(2-hydroxyphenyl)-1-S-(2-hydroxyethylthio)methane.
A generalized procedure for the reaction of a free mercaptan with a glycidyl ether is as follows:
To a stirred mixture of the mercaptan and acid catalyst under nitrogen atmosphere is added the glycidyl ether, either neat or in solution, while maintaining the temperature between 25xc2x0-60xc2x0 C. The mixture or solution is then heated to between 50xc2x0-75xc2x0 C. for a period of 1 to 6 hours and conversion to product is monitored by gas chromatography and iodine titration for %SH. The acid catalyst is removed by alkaline wash, the resulting product is dried with magnesium sulfate, and filtered. The solvent, if required, is removed under reduced pressure at  less than 550 C to yield the latent mercaptan. For example, the reaction between mercaptoethanol and glycidyl neodecanoate gives C9H19C(xe2x95x90O)OCH2CH(OH)CH2SCH2CH2OH. This procedure is referred to hereinafter as Procedure D.
A generalized procedure for the condensation of a free mercaptan with an aldehyde is as follows:
To a stirred solution of the mercaptan, acid catalyst, and azeotropic solvent under nitrogen atmosphere is added the aldehyde with heating to reflux, typically between 65xc2x0-120xc2x0 C., for removal of reaction water. Completion of reaction is achieved after the theory amount of water has been collected. Optionally, to a stirred solution of mercaptan, aldehyde, and ether is added BF3-etherate dropwise under reflux conditions. The solution is refluxed for between 1 to 6 hours and conversion to product is monitored by gas chromatography. The acid catalyst is removed by alkaline wash, the solution is dried with magnesium sulfate and filtered. The solvent is removed under reduced pressure at  less than 65xc2x0 C. to yield the latent mercaptan. This generalized procedure is referred to hereinafter as Procedure E.
The polarized, unsaturated compounds are exemplified by 3,4-dihydropyran; 3,4-dihydro-2-methoxy-2H-pyran; 3,4-dihydro-2-ethoxy-2H-pyran; 3,4-dihydro-2-methoxy-2H-pyran; 3,4-dihydro-2-formyl-2H-pyran; 3,4-dihydro-3-methoxy-2H-pyran; and 2,3-dihydrofuran. The 3,4-dihydro-2-formyl-2H-pyran is made by the Diels-Alder dimerization of acrolein at high temperatures and pressures. The 3,4-dihydro-2-alkoxy-2H-pyrans and 3,4-dihydro-2-phenoxy-2H-pyran are made by the reaction of the corresponding vinyl ether with acrolein in the presence of a catalytic amount of a zinc salt, e.g., zinc chloride. A variety of 3,4-dihydro-2H-pyrans having a substituent in the 2-position can be made by similar reactions. The products formed by the reaction of 1 and 2 moles of acrolein with the divinyl ether of an alkylene- or polyalkylene glycol are blocking agents, also. In the case of the reaction of two moles of acrolein per mole of a divinyl ether, latent mercaptans made from the resulting di-(3,4-dihydropyranyl) ethers also have the potential of being chelating agents in the polymer compositions of this invention. The reaction of one mole of acrolein with one mole of the divinyl ether forms a monomer which may be copolymerized with vinyl chloride with or without a wide variety of ethylenically unsaturated compounds. The product from the reaction of acrolein with chloroethyl vinyl ether provides a substituted 3,4-dihydropyran that can be further derivatized.
A stabilizer composition of this invention may be made quite conveniently by the addition of a mercaptan across the double bond of the pyran ring in the presence of zinc chloride as a catalyst for the addition and as a synergistic stabilizer in the product.
Examples of 2-S-(tetrahydropyranyl)thioalkanols that are suitable as latent mercaptans for this invention include, without limitation, 2-S-(tetrahydropyranyl)thioethanol, 2-S-(tetrahydropyranyl)thiopropanol, and 2-S-(tetrahydropyranyl)thiobutanol 6-S-(2-formyl-tetrahydropyranyl)thioethanol, and their furanyl homologs, e.g., 5-S-(tetrahydrofuranyl)thioalkanol. The carboxylates suitable for the purposes of this invention are exemplified by 2-S-(tetrahydropyranyl)thioethyl caprate, which also may be named 2-S-(2-decanoyloxyethylthio)tetrahydropyran, made by the reaction between mercaptoethyl caprate and 3,4-dihydropyran according to the foregoing procedure and has the following formula: 
Homologs of the thus described compounds which are particularly useful in the stabilization of flexible PVC compositions include the 2-S-(tetrahydropyranyl)thioalkyl carboxylates and their furanyl homologs wherein the ethyl moiety is replaced by propyl, butyl, hexyl, and others in the series up to and including dodecyl and the capric acid radical of said compound is replaced by other fatty acid radicals (saturated and unsaturated) or resin acid radicals having up to and including 22 carbon atoms. The acids are exemplified by caproic, caprylic, lauric, myristic, palmitic, stearic, arachidic, behenic, and the oleic and linoleic acids, as such, or as found in tall oil acids along with abietic and pimaric acids. The mercaptoalkyl carboxylate moiety is thus exemplified by mercaptoethyl laurate, mercaptoethyl oleate, mercaptoethyl hexanoate, mercaptoethyl octanoate, mercaptoethyl myristate, mercaptoethyl palmitate, mercaptoethyl stearate, mercaptoethyl oleate, mercaptoethyl linoleate, and the mercaptopropyl, mercaptobutyl, and mercaptooctyl homologs of each of the above. The esters are made by the conventional method of reacting the hydroxyl group of a mercaptoalkanol with the desired carboxylic acid in the presence of an acidic catalyst and removing water as it forms.
When 2-S-tetrahydropyranylthioethanol is prepared from 3,4-dihydropyran by said procedure, by-products having the following formulas are also obtained: 
The homologous by-products are expected when 2,3-dihydrofuran is reacted with mercaptoethanol but the principal product is the 5-S-tetrahydrofuranylthioethanol shown by the following structure: 
When the 3,4-dihydropyran is replaced by a 3,4-dihydro-2-alkoxy-pyran; a 3,4-dihydro-2-phenoxy-pyran; or a 3,4-dihydro-2-formyl-pyran in the above procedure, the following products are formed: 
A 2-S-(tetrahydropyranyl)mercaptoalkyl carboxylate is more active as a heat stabilizer in flexible PVC compositions than the tetrahydropyranyl-blocked mercaptans derived from alkylmercaptans such as dodecanethiol when activated according to this invention as manifest in the improved color hold properties and dynamic thermal stability of such stabilized PVC compositions. The higher activity may be the result of the better compatibility of the ester-containing latent mercaptans with a plasticized PVC. The compatibility of the corresponding homologous furan-based latent mercaptans is similar.
As used herein, a zinc ionomer is defined as a salt in which both of the zinc valences are paired with carboxylate anions from the oxidized polyethylene, a mixed salt in which one of the zinc valences is paired with a carboxylate ion having from 7 to 18 carbon atoms and the other is paired with a carboxylate ion from an oxidized polyethylene, or a physical mixture of a zinc salt of a carboxylic acid having from 7 to 18 carbon atoms and a zinc salt an oxidized polyethylene. For the purposes of this invention, the oxidized polyethylene has a molecular weight of at least about 750 and up to about 2100. The oxidized polyethylenes have from about 50 to about 150 carbon atoms and are believed to have hydroxyl and ketonic substituents along the polymer chain as well as carboxylic groups. The acid number ranges from about 2 to about 50. The melting point of the oxidized polyethylene is preferably from about 60xc2x0 C. to 150xc2x0 C. (140-302xc2x0 F.) so that it is solid at the temperatures at which vinyl chloride resins are normally used. A preferred oxidized polyethylene, sold by Allied-Signal Corp. as AC629A, has molecular weight of about 2000, a softening point in the 213-221xc2x0 F. (101-105xc2x0 C.) range, and an acid number of 14-17.
The carboxylic acids that are useful along with the oxidized polyethylene may be aliphatic, arylaliphatic, aromatic, or alkylaromatic; the aliphatic moieties have a straight or branched chain structure and may be saturated or unsaturated. Thus, the mixed salt may include an anion from, for example, heptanoic, octanoic (or caprylic), 2-ethylhexanoic, decanoic (or capric), lauric, oleic, stearic, benzoic, phenylacetic, or methylbenzoic acid. An ionomer wherein the octanoate and the oxidized polyethylene fulfill the zinc valences is an example of a preferred latent wetting agent for the vinyl chloride resin.
The stoichiometric amount of zinc oxide, zinc chloride, or a zinc carboxylate/chloride is reacted with the oxidized polyethylene to prepare the desired zinc salt. The zinc carboxylate/chloride is prepared from zinc chloride and less than the stoichiometric amount of the desired carboxylic acid so that the remaining chloride ions may react with the oxidized polyethylene to form a mixed salt as an ionomer useful in this invention. An ionomer is also made by the stepwise reaction of the zinc oxide with the oxidized polyethylene and, for example, octanoic acid or by a one step reaction with a mixture of the oxidized polyethylene and octanoic acid.
The adhesion promoting stabilizer compositions of this invention consist essentially of from about 40% to about 98%, preferably from about 60% to about 80% of a latent mercaptan and from about 2 to about 60%, preferably from about 20 to about 40%, of the zinc ionomer, based on the total weight of the stabilizer composition. The latent mercaptan is exemplified by 2-S-(tetrahydropyranyl)thioalkanol, a carboxylate thereof, a 2-S-(tetrahydrofuranyl)-thioalkanol, a carboxylate thereof, a 2-S-(tetrahydropyranyl)thiocarboxylic acid, an ester thereof, a 2-S-(tetrahydrofuranyl)thiocarboxylic acid, an ester thereof, and a mixture of two or more of said alkanols, acids, and esters. They are particularly suited to impart superior stabilization against the deteriorative effects of heat and ultra-violet light on flexible PVC resins in comparison with stabilizer compositions previously known in the art. They may be prepared by blending the components thereof in any convenient manner which produces a homogeneous mixture, such as by shaking or stirring in a container. Likewise, the stabilizer compositions of this invention can be incorporated in a vinyl chloride resin in an appropriate mill or mixer or by any other of the well-known methods which provide uniform distribution of the stabilizer throughout the polymer composition.
It will be readily apparent to one of ordinary skill in the art, that the precise amount of stabilizer composition added to the vinyl chloride resin will depend upon several factors, including, but not limited to, the particular resin employed, the temperature to which the resin will be subjected, and the possible presence of other stabilizing compounds. In general, the more severe the conditions to which the resin is subjected, and the longer the term required for resisting degradation, the greater will be the amount of stabilizer composition required. Generally, the stabilizer composition is used in an amount to provide as little as about 0.20 part and as much as about 5 parts by weight of the latent mercaptan per hundred parts by weight (phr) of the PVC resin. While there is no critical upper limit to the amount of latent mercaptan which can be employed, amounts up to about 3.0 phr of the PVC resin are preferred. The zinc salt of oxidized polyethylene is used in an amount effective to improve the wettability to water-based paints and inks of an article formed from the vinyl chloride resin. From about 0.2 to about 2.5 phr is suitable, but from 0.5-1.5 phr is preferable.
In addition to the stabilizer compositions of this invention, the PVC resin compositions of this invention may contain plasticizers, as mentioned above in regard to semi-rigid and flexible PVC, as well as pigments, fillers, antioxidants, blowing agents, dyes, ultraviolet light absorbing agents, densifying agents, biocides, and the like.
Conventional non-metallic stabilizers can also be included in the PVC resin compositions of the present invention. Thus, there can be included 0.01-0.75%, based on the weight of the resin, of sulfur containing compounds such as dilauryl-thiodipropionate, distearyl 3,3xe2x80x2-thiodipropionate, dicyclohexyl-3,3-thiodipropionate, dioleyl-3,3xe2x80x2-thiodipropionate, dibenzyl-3,31xe2x80x2-thiodipropionate, didecyl-3,3xe2x80x2-thiodipropionate, dibenzyl-3,3xe2x80x2-thiodipropionate, diethyl-3,3xe2x80x2-thiopropionate, lauryl ester of 3-methylmercaptopropionic acid, lauryl ester of 3-butylmercaptopropionic acid, lauryl ester of 3-lauryl mercaptopropionic acid, and phenyl ester of 3-octyl mercaptopropionic acid.
Likewise there can be included from 0.01-10% by weight of the vinyl chloride polymer of a polyol stabilizer for vinyl chloride resins. Thus there can be included glycerol, sorbitol, pentaerythritol, mannitol and polyethers such as diethylene glycol, triethylene glycol, tetraethylene glycol, tripropylene glycol, and the like.
Nitrogen containing stabilizers such as dicyandiamide, melamine, urea, formoguanamine, dimethyl hydantoin, guanidine, thio-urea, 2-phenylindoles, aminocrotonates, N-substituted maleimides, uracil, the 1,3-dialkyl-6-amino-uracil derivatives described in German Offenlegungsschrift 19,741,778 by Ciba Specialty Chemicals Holding Inc., and the pyrrolodiazine diones described in published Australian Patent Application No. AU-A-48232/96 by Ciba-Geigy, and the like may also be included in the compositions of this invention in amounts of 0.1-10% by weight.
The 1,3-dialkyl-6-amino-uracils and 1,3-dialkyl-6-phenylamino uracils are prepared by known methods such as those taught in U.S. Pat. No. 2,598,936, which is incorporated herein by reference. Other uracils suitable for use in this invention have substituents such as hydroxyalkyl, alkoxyalkyl, hydroxyphenyl, etc. and are taught in U.S. Pat. No. 4,656,209, which is incorporated herein by reference, also. They, also, may be made according to the procedures of the 936 patent. Their structure is illustrated by the following formula: 
wherein R*, and **R, are independently hydrogen, alkyl, hydroxyalkyl, or alkoxyalkyl, and R*** is hydrogen, alkyl, phenyl, or hydroxyphenyl, wherein each of the alkyl moieties have from 1 to 4 carbon atoms.
Of particular interest are the pyrrolodiazine diones described by the formula: 
wherein R⋄, R2⋄, R3⋄, and R4⋄ are independently hydrogen or C1-C4 alkyl. Examples of compounds contemplated for use in this invention include the 1H-pyrrolo[2,3-d]pyrimidine-2,4(3H,7H)diones exemplified by Compound Nos. 103, 111, 123, 129, and 131 of said Australian Patent Application, which have the following substituents:
No. 103 1,3,6-trimethyl;
No. 111 1,3,6,7-tetramethyl;
No. 123 none;
No. 129 1,3-diethyl,6-methyl;
No. 131 1,3-di-n-butyl,6-methyl;
Said compounds may be prepared by the method described by S. Senda and K. Hirota, Chem. Pharm. Bull., 22(7), 1459-1467(1974) or by the reaction of the corresponding aminouracil with molar excesses of chloroacetaldehyde and ammonium acetate in water at about 65xc2x0 C. until a precipitate forms or with molar excesses of acetoxyacetone and ammonium acetate in water at reflux for 12 hours.
An anti-oxidant may be added in an amount of 0.01-10%, preferably 0.1-5% by weight of the PVC resin. Phenolic anti-oxidants are particularly suitable and are exemplified by 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, propyl gallate, 4,4xe2x80x2-thiobis(6-t-butyl-m-cresol), 4,4xe2x80x2-cyclohexylidene diphenol, 2,5-di-t-amyl hydroquinone, 4,4xe2x80x2-butylidene bis(6-t-butyl-m-cresol), hydroquinone monobenzyl ether, 2,2xe2x80x2-methylene-bis(4-methyl-6-t-butyl phenol), 2,6-butyl-4-decyloxy phenol, 2-t-butyl-4-dodecyloxy phenol, 2-t-butyl-4-dodecyloxy phenol, 2-t-butyl-4-octadecyloxy phenol, 4,4xe2x80x2-methylene-bis(2,6-di-t-butyl phenol), p-amino phenol, N-lauryloxy-xcex2-amino phenol, 4,4xe2x80x2-thiobis (3-methyl-6-t-butyl phenol), bis[o-(1,1,3,3-tetramethyl butyl)phenol]sulfide, 4-acetyl-xcex2-resorcylic acid, A-stage p-t-butylphenolformaldehyde resin, 4-dodecyloxy-2-hydroxybenzophenone, 3-hydroxy-4-(phenylcarbonyl) phenyl palmitate, n-dodecyl ester of 3-hydroxy-4-(phenyl carbonyl) phenoxyacetic acid, and t-butyl phenol.
From 0.01-30% by weight of an epoxy compound, based on the weight of the vinyl chloride polymer in the PVC compositions of this invention may also be used. Examples of such epoxy compounds include epoxidized soya bean oil, epoxidized lard oil, epoxidized olive oil, epoxidized linseed oil, epoxidized castor oil, epoxidized peanut oil, epoxidized corn oil, epoxidized tung oil, epoxidized cottonseed oil, epichlorhydrin/bis-phenol A resins, phenoxy-propylene oxide, butoxypropylene oxide, epoxidized neopentylene oleate, glycidyl epoxystearate, epoxidized xcex1-olefins, epoxidized glycidyl soyate, dicyclopentadiene dioxide, epoxidized butyl toluate, styrene oxide, dipentene dioxide, glycidol, vinyl cyclo-hexene dioxide, glycidyl ether of resorcinol, glycidol ether of hydroquinone, glycidyl ether of 1,5-dihyroxynaphthalene, epoxidized linseed oil fatty acids, allyl glycidyl ether, butyl glycidyl ether, cyclohexane oxide, 4-(2,3-epoxypropoxy) aceto-phenone, mesityl oxide epoxide, 2-ethyl-3-propyl glycidamide, glycidyl ethers of glycerine, pentaerythritol and sorbitol, and 3,4-epoxycyclohexane-1,1-dimethanol bis-9,10-epoxystearate.
Likewise there can be used organic phosphites in an amount of 0.01 to 10%, preferably 0.1-5% by weight of the vinyl chloride polymer. The organic phosphites contain one or more, up to a total of three, aryl, alkyl, aralkyl and alkaryl groups, in any combination. The term xe2x80x9ctrialkylarylxe2x80x9d is inclusive of alkyl, aryl, alkaryl and aralkyl phosphites containing any assortment of alkyl, aryl, alkaryl and aralkyl groups. Exemplary are triphenyl phosphite, tricresyl phosphite, tri(dimethylphenyl) phosphite, tributyl phosphite, trioctyl phosphite, tridodecyl phosphite, octyl diphenyl phosphite, dioctyl phenyl phosphite, tri(octyl-phenyl) phosphite, tri(nonylphenyl) phosphite, tribenzyl phosphite, butyl dicresyl phosphite, octyl di(octyl-phenyl) phosphite, tri(2-ethyl-hexyl) phosphite, tritolyl phosphite, tri(2-cyclohexylphenyl) phosphite, tri-alpha-naphthyl phosphite, tri(phenylphenyl) phosphite, and tri(2-phenylethyl) phosphite.
Conventional lubricants for vinyl chloride resins such as low molecular weight polyethylene, i.e. polyethylene wax, fatty acid amides, e.g. lauramide and stearamide, bisamides, e.g. decamethylene bis amide, and fatty acid esters, e.g. butyl stearate, glyceryl stearate, linseed oil, palm oil, decyloleate, corn oil, cottonseed oil, hydrogenated cottonseed oil, stearic acid, calcium stearate, mineral oil, montan wax, and the like can also be included.
The latent mercaptans having the following formula (Formula 2 are considered to be novel compositions of matter that are useful with or without the zinc ionomers as a heat-stabilizer for halogen-containing polymers 
wherein a is 0 or 1, m is 0 or 1, and n is 0 or 1; y=1 to 4, when y=1, z is 1 to 4, when y is more than 1 z is 1; R1 is Rxe2x80x2C(O)OH wherein Rxe2x80x2 is an alkylene radical, or R1 is a thio-[bis (alkoxycarbonylalkyl)], dithio-[bis(alkoxycarbonylalkyl)], pentaerythrityl, alkenyloxy(polyalkoxy)alkyl, oxy[bis(alkoxyacyl)], oxy[bis(polyalkoxycarbonylalkyl ], benzoyloxy(polyalkoxy)alkyl, or benzoyloxy(polyalkoxy)acyl radical, said alkyl, alkylene, and acyl radicals having from 1 to 22 carbon atoms; R2, R3, R4, R5, R6, and R7 are independently hydrogen, a hydroxyl, mercapto, alkyl, alkylenyl, acyl, aryl, haloaryl, alkaryl, aralkyl, hydroxyalkyl, chloroalkoxy, alkylene, alkenyloxyalkoxy, alkoxy, aryloxy, alkaryloxy, mercaptoalkyl, hydroxyalkylmercaptoalkyl, mercaptoalkylenyl, hydroxyaryl, alkoxyaryl, alkoxyhydroxyaryl, arylcarbonyl, or mercaptoaryl radical having from 1 to 22 carbon atoms; X is aryl, haloaryl, alkaryl, hydroxyaryl, dihydroxyaryl, aralkaryl, alkoxyaryl, arylcycloalkyl, or a heteroatom selected from the group consisting of oxygen and sulfur, with the option that one or both of the R3 and R5 alkylenyl radicals joins with R7 and X to form a heterocyclic moiety with X as the heteroatom.
It has also been found that a one-component PVC stabilizer is obtained from the latent mercaptans of Formula 1 and Formula 2 wherein R1 is pentaerythrityl by forming a complex with a zinc halide. For example, a zinc halide forms a complex with a pair of neighboring hydroxyl groups in a latent mercaptan such as the adduct of 2 moles of 3,4-dihydropyran with one mole of the diester of pentaerythritol and a mercaptocarboxylic acid such as thioglycolic acid or mercaptopropionic acid. The one-component PVC stabilizer is pre-formed or formed in situ by complexing a zinc halide, preferably the chloride, with such a latent mercaptan as shown by the following formula: 
wherein Hal is a halogen ion, preferably a chloride ion. The preparation of blocked mercaptans and zinc salts used in the adhesion promoting stabilizers of this invention, the preparation of said stabilizers, and the advantages of compositions comprising said stabilizers are illustrated as follows.
1H-NMR spectroscopy was used to determine the molecular structure of 2-S-(decanoyloxyethylthio)tetrahydropyran or 2-S-(tetrahydropyranyl)thioethylcaprate which was prepared by adding 42.0 grams (0.50 mole) of 3,4-dihydropyran to 112.2 grams (0.50 equivalent) of mercaptoethylcaprate (14.7% SH) in the presence of an acid catalyst over a period of 45 minutes while maintaining a nitrogen atmosphere and a temperature below 35xc2x0 C. and then heating it to 50xc2x0 C. and holding that temperature for 1.5 hours. After cooling the solution, it was washed with two 200 ml portions of a 10% sodium bicarbonate solution in water, followed by a 200 ml wash with water. The organic layer was dried with MgSO4 to yield a light yellow liquid having an SH content of less than 0.5 percent as determined by titration with a 0.100 N iodine solution in isopropanol. The 1H-NMR (CDCl3, xcex4) spectrum was: 2.3 (2H, t, xe2x80x94C(xe2x95x90O)xe2x80x94CH2xe2x80x94CH2), 2.8 (2H, m, xe2x80x94Sxe2x80x94CH2xe2x80x94CH2xe2x80x94), 4.2 (2H, m, xe2x80x94Sxe2x80x94CH2CH2xe2x80x94Oxe2x80x94), 4.9 (1H, m, xe2x80x94Oxe2x80x94CH(xe2x80x94Sxe2x80x94CH2xe2x80x94)xe2x80x94CH2xe2x80x94CH2xe2x80x94). The total color change (dE) of a PVC composition containing 0.13 phr of the latent mercaptan of this example was measured versus a white tile standard using a Hunter calorimeter at one minute intervals. At one minute, it was 4.2; at five minutes, it was 8.4.
2-S-tetrahydropyranyl)thioethyltallate was prepared by adding 172.45 grams (2.05 equiv.) of 3,4-dihydro(2H)pyran dropwise to 760.00 grams (2.00 equiv.) of 2-mercaptoethyltallate (8.70% SH by iodometric titration) containing 0.93 gram of methanesulfonic acid (70% active) over a period of 45 minutes under a nitrogen blanket and a temperature between 25-35xc2x0 C. and heating to 35-40xc2x0 C. for 2 hours. After cooling the solution, 3 grams of Norite carbon black was charged and the product was vacuum filtered to yield 932 grams of yellow liquid having a SH content of less than 0.4% as determined by titration with 0.100 N iodine solution in isopropanol. The 1H-NMR(CDC13, xcex4) spectrum was: 2.3 (2H, t, xe2x80x94C(xe2x95x90O)xe2x80x94CH2xe2x80x94CH2xe2x80x94), 2.8 (2H, m, xe2x80x94Sxe2x80x94CH2xe2x80x94CH2xe2x80x94), 4.3 (2H, m, (xe2x80x94CC(xe2x95x90O)xe2x80x94Oxe2x80x94CH2), 4.9 (1H, m, xe2x80x94Oxe2x80x94CH(xe2x80x94Sxe2x80x94CH2)xe2x80x94CH2xe2x80x94CH2xe2x80x94). GC of the product (1% in ether) indicated one primary product peak at 26.3 minutes retention time (50-300xc2x0 C.; 10xc2x0 C./min.; split flow injector/FID). The product is referred to in Table 1 below as DHP/2-MET.
To a 250 ml flask fitted with a side-arm condenser there was charged with stirring 50 grams (0.0143 equivalent) of oxidized polyethylene (Allied Signal AC-629A), 175 ml of butyl carbitol, 1.16 grams (0.0286 equivalent) of 99% pure zinc oxide, and 2.06 grams (0.0143 equivalent) of 99% pure octanoic acid. The reaction mixture was then heated to 75xc2x0 C. (167xc2x0 F.) and 3 drops of glacial acetic acid were added before the temperature was raised to 120-125xc2x0 C. (248-257xc2x0 F.) for 20 minutes. The mixture was stripped of water and solvent by applying a vacuum of 3 mm Hg at that temperature. The product is a cream-colored wax which has a zinc content of 1.8% (measured as the metal) according to atomic absorption analysis. The theoretical zinc content is 1.8%. The product is referred below as ZNION.